Pump

ABSTRACT

A HOUSING HAVING THREE IN-LINE CYLINDRICAL OPENINGS FORMED THEREIN WITH AN OUTLET AND INLET IN COMMUNICATION WITH EACH OF SAID OPENINGS, AN INSERT POSITIONES IN EACH OF SAID OPENINGS FOR FORMING OUTELT VALUE MEANS, A SECOND INSERT POSITIONED IN EACH OF SAID OPENINGS FOR FORMING INLET VALVE MEANS, PACKING POSITIONED IN EACH OF SAID OPENINGS AND COOPERATING WITH THE INSERTS TO DEFINE A CYLINDER, AND A PLUNGER MOUNTED IN EACH OF SAID CYLINDERS FOR RECIPROCATING MOVEMENTS. THE FURTHER IMPROVEMENT INCLUDING MEANS SUBJECT TO FLUID OUTLET PRESSURE OPERATING ON THE PACKING TO MAINTAIN A COMPRESSION FORCE ON SAID PACKING. SAID THREE PLUNGERS BEING RECIPROCATED SINUSOIDALLY BY MEANS OF ECCENTRIC MEMBERS ATTACHED TO A DRIVE SHAFT.

y 30, 1972 R. F. RASMUSSEN 3,666,382

PUMP

Filed March 24 1970 3 Sheets-Sheet 1 mvsmoa ROBERT F. Rasmussen:

HTTORNEYS May 30, 1972 R. F. RASMUSSEN PUMP 3 Sheets-Sheet 3 Filed March24 1970 fins. 9

its. 7

INVENTOR. ROBERT E. RHSMUSSEN ATTORNEYS United States Patent Oflice-3,666,382 Patented May 30, 1972 3,666,382 PUMP Robert F. Rasmussen,Minneapolis, Minn., assignor to Roseville Engineering, Inc., St. Paul,Minn. Continuation-impart of application Ser. No. 810,681,

Mar. 26, 1969. This application Mar. 24, 1970, Ser. No. 22,176

Int. Cl. F16j 15/00; F04b 21/02, 39/10 US. Cl. 417-533 12 ClaimsABSTRACT OF THE DISCLOSURE A housing having three in-line cylindricalopenings formed therein with an outlet and inlet in communication witheach of said openings, an insert positioned in each of said openings forforming outlet valve means, a second insert positioned in each of saidopenings for forming inlet valve means, packing positioned in each of-said openings and cooperating with the inserts to define a cylinder,and a plunger mounted in each of said cylinders for reciprocatingmovements. The further improvement including means subject to fluidoutlet pressure operatmg on the packing to maintain a compression forceon said packing. Said three plungers being reciprocated sinusoidally bymeans of eccentric members attached to a drive shaft.

BACKGROUND OF THE INVENTION This application is a continuation-in-partof US. application Ser. No. 810,681, filed Mar. 26, 1969, now abandoned.

Field of the invention to force it out of the cylinder during movementin the opposite direction.

Description of the prior art In general, prior art pumps of the typedescribed are complicated and expensive to produce since many operationsare required on the housing to form inlet and outlet valves andcylinders therein. In addition, these prior art pumps generally must beconstructed entirely of a material compatible with the fluid beingpumped so that no chemical interaction takes place therein. Becauseinlet and outlet ports and valves are formed in the housing, these priorart pumps are complicated and time consuming to assemble. Further, somemulti-cylinder pumps, wherein the plungers move sinusoidally, have beenconstructed but they are complicated and unaccommodating tononlubricating fluids. One example of such a pump is disclosed in US.Patent 3,169,488 issued to Galliger.

SUMMARY OF THE INVENTION The present invention pertains to an improvedpump having a housing which defines an elongated opening incommunication with inlet and outlet ports and insert means positioned inthe opening for defining inlet and outlet valve means in communicationwith the inlet and outlet ports and further defining a cylinder with aplunger positioned therein for reciprocating movements.

It is an object of the present invention to provide an improved pumpproduced by forming a cylindrical opening in a housing and positioningvalve means in the cylindrical opening to define inlet and outlet valvesand a cylinder for receiving a plunger therein.

It is a further object of the present invention to provide a pump inwhich the housing is produced with a head formed of material chemicallycompatible with a fluid being pumped and the base is formed of arelatively inexpensive material.

It is a further object of the present invention to provide an improvedpump wherein packing means encircle the plunger to prevent leakage offluid into the base of the housing and the packing is maintained in acompressed position by use of compression springs or means subject tothe fluid pressure in the outlet port of the pump.

It is a further object of the present invention to provide an improvedpump having at least three in-line cylinders with plungers thatreciprocate sinusoidally, to provide a net output pressure that isrelatively constant.

It is a further object of the present invention to provide an improvedpump which is relatively inexpensive and simple to produce and assemble.

These and other objects of this invention will become apparent to thoseskilled in the art upon consideration of the accompanying specification,claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation ofan embodiment of the improved pump;

FIG. 2 is a sectional view as in FIG. 1;

FIG. 3 is an enlarged view in side elevation, portions thereof brokenaway and shown in section;

FIG. 4 is an enlarged sectional view as seen generally from the line 44in FIG. 3, portions thereof broken away;

'FIG. 5 is an enlarged sectional view similar to FIG. 4 illustratinganother embodiment, portions thereof broken away;

FIG. 6 is an enlarged exploded view in perspective of a portion of theapparatus illustrated in FIG. 5;

FIG. 7 is a graphic representation of the output flow rate of the threecylinders, the dotted lines indicating individual cylinder flow ratesand the full line indicating the total flow rate of the improved pump;

FIG. 8 is a graphic representation of the total flow rate of theimproved pump, in dotted line, compared to the total fiow rate of a pumputilizing short connecting rods to drive the plungers;

FIG. 9 is an enlarged sectional view similar to FIG. 4 of anotherembodiment of the improved pump, portions thereof removed; and

FIG. 10 is a view similar to FIG. 7 illustrating a different position ofthe mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. l-4 the numeralhousing having a head 11 and embodiment the housing seen from the line22 their associated parts, but it should be understood that any desirednumber of cylinders might be utilized in the present pump. The head 11and base 12 are fixedly attached together by means of a plurality ofbolts 13 inserted through openings in projecting portions of the head 11and threadedly engaged into the base 12. In the following description ofthe figures, the terms upper and lower are utilized to describe thevarious parts illustrated, although it should be understood that in someinstances these are not limiting and the pump might be used inorientations other than that shown.

The head 11 has formed in the upper wall thereof an inlet port 15 whichis adapted to have conduit threadedly engaged therein for conveyingfluid to be pumped. An outlet port 16 is formed at one end of the head11 and adapted to have conduit threadedly engaged therein for conveyingthe fluid away from the pump. Three cylindrical openings generallydesignated 17 are formed in the head 11 in parallel, longitudinallyspaced apart relationship so as to extend generally transverse to thelongitudinal dimension of the head 11 and open axially outwardly (ordownwardly in the figures) at the junction of the head 11 and the base12. This particular orienta tion of the cylindrical openings is referredto as an in-line configuration hereinafter. A first elongated cavity 18formed adjacent the upper wall of the head 11 communicates with theinner end of each of the cylindrical openings 17 and with the inlet port15. A second elongated cavity 19 extending generally parallel with thecavity 18 and spaced axially outwardly (or downwardly in the figures)therefrom communicates with each of the cylindrical openings 17 and withthe outlet port 16. While the head 11 might be formed in a variety ofways the presently disclosed embodiment is formed by casting and bymachining the cylindrical openings 17 to fit the various components tobe described presently.

Each of the cylindrical openings 17 has a radially in wardly extendingflange 20 adjacent the axially inner extremity (or upper end) thereofand defined by the lower wall of the cavity 18. A generally cup-shadedinsert 21 is provided with a plurality of openings 22 therethrough and aflexible valve member 23 aflixed to the insert 21 by a centrally locatedbolt 24. The valve member 23 has a diameter such that it overlies theopenings 22 and a spring 25, fixed in position by the bolt 24, biasesthe valve member 23 against the insert 21 to maintain the openings 22normally closed. The assembly including the insert 21 is fitted into theaxially inner end of the cylindrical opening 17 in abutting engagementwith the flange 20. In this position the openings 22 are incommunication with the cavity 18.

A second generally tubular insert 30 is formed with a first portionhaving an outer diameter approximately equal to the outer diameter ofthe insert 21 and adapted to mate therewith. An O-ring 31 is positionedbetween the mat'mg portions of the insert 21 and the insert 30 toprevent leakage therebetween. Adjacent the axially outer end of theportion of insert 30 just described is a radially inwardly directedportion having a plurality of openings 32 extending therethrough in adirection approximately parallel with the direction of the cylindricalopening 17. A third portion of the insert 30 extends generally coaxialwith the cylindrical opening 17 from the inner edges of the radiallyinwardly direction portion of the insert 30. The openings 32 in theinsert 30 communicate with the cavity 19 and with the cavity formedwithin the inserts 30 and 21. A flexible ring or valve member 33, havingan inner diameter slightly larger than the outer diameter of the lowerportion of insert 30 for easy axially sliding movements thereon and anouter diameter sufficiently large to overlie the openings 32, isslidably engaged over the insert 30 to operate as a valve in conjunctionwith the openings 32.

A generally tubular insert or packing cartridge 40 is positioned in thecylindrical opening 17 in parallel juxtaposition with the inner wallsthereof and with an axially inner edge butting against a radiallyinwardly directed shoulder 41 in the inner wall of the cylindricalopening 17. The shoulder 41 positions the packing cartridge 40 withinthe cylindrical opening 17 so that the various springs and valves canoperate properly. The insert 40 has a radially inwardly directed flangethereon which engages the axially outer end of the insert 30 to maintainthe insert 30 in the correct position. O-rings 42 and 43 are positionedbetween the insert 30 and the packing cartridge 40 and between thepacking cartridge 40 and the head 11 to prevent leakage axially alongthe sides thereof. A spring 34, positioned between the axially inner endof the insert 40 and the valve member 33, biases the valve member 33against the insert 30 to normally maintain the openings 132 closed.

Sealing means, which in this embodiment is pump packing 45, ispositioned coaxially within the packing cartridge 40 axially outwardlyfrom the insert 30. A metal ring-shaped packing follower 46 engages theupper surface of the packing 45 and a spring 47 positioned between thepacking follower 46 and the flange of the packing cartridge 40 biasesthe packing follower 46 against the packing 45 to maintain compressionthereon. A ring-shaped packing seat 48 engages the lower surface of thepacking 45 and is held fixedly in position by means of an insert 49.

Insert 49 has a generally tubular configuration with the inner diameterthereof approximately equal to the inner diameter of the packing 45 andthe insert 30. An O-ring 50 is positioned between the upper edge of theinsert 49 and the lower edge of the packing seat 43 to prevent leakagetherebetween. The insert 49 forms an upper bearing for a plunger 55,which is positioned in the cylinder formed by packing 45 and insert 30.

It will be appreciated that the components numbered 2125, 30-34 and40-50 together define a unitary, removable assembly (best seen in FIG.3) which, by simple insertion into the receptacle defined in head 11provides an inlet check valve communicating with the inlet chamber orcavity 18 through its associated opening 17, an outlet check valvecommunicating with the outlet chamber 19, and a cylindrical pumpingchamber in which plunger 55 may reciprocate. It will also be appreciatedthat, by reason of the several shoulder abutment surfaces between theinsert assembly and its receptacle, the head 11 and base 12 cooperate torigidly retain the insert assembly in operating position; and thatremoval of the assembly is quickly and easily effected by removal of thebolts 13 and lifting head 11 from base 12. Since the fluid pumped isalways isolated from the base 12 and plunger reciprocating mechanism bythe improved structure, it is possible. to adapt a given pump to a givenfluid simply by changing the insert assemblies and/or head 11.

The plunger 55 has a snap-ring 56 positioned in a groove spaced axiallyfrom the lower edge of the insert 49 and a ring-shaped spring seat 57 iscoaxially positioned over the plunger 55 in abutting engagement with thesnap-ring 5'6. A compression spring 58 is positioned between a radiallyoutwardly directed flange of the insert 49 and the spring seat 57 tobias the plunger 55 axially outwardly in the cylindrical opening 17.

The base 12 of the housing 10 is generally hollow except for a wall 68adjacent the upper extremity thereof and extending generally transverseto the cylindrical openings 17 in the head 11 (with the head 11 and base12 fixedly attached), and a second wall 61 parallel with the first wall60 and spaced therefrom into the base 12. Pairs of openings 62 and 63are formed in the walls 60 and 61 generally coaxial with each of thecylindrical openings 17 in the head 11. The lower opening 63 has aninsert 64 therein with an inner wall that slidably engages the outerwall of the plunger 55 and serves as a lower bearing therefor. The upperwall 60 engages the axially outer or lower edge of the upper bearing 49and holds it fixedly in place in abutting engagement with the packingseat 48 and the packing cartridge 40. Thus, all of the variouscomponents in the cylindrical openings 17 of the head 11 are maintainedin their correct orientation.

In the event the packing 45 and/or some of the other components in thehead 11 become worn after extended use, some leakage of the fluid beingpumped may occur before the wear is noticed by an operator. To preventthis leaking fluid from entering the base 12 vents 69 are providedadjacent the juncture of the head 11 and base 12. The vents 69 consistof at least one external opening for each cylindrical opening 17,adjacent the juncture and at least one radially inwardly extendinggroove formed between the axially outer edges of the packing cartridge40 and the packing follower 48 and the mating edge of the insert 49. TheO-ring 50 prevents leaking fluid from continuing axially along theplunger 55 and directs externally through the vents 69.

A cavity 70 is formed in the base 12 between the wall 61 and the lowerwall thereof. The base 12 has a large opening 71 at one end thereof incommunication with the cavity 70 for the assembly of the pump and asmaller opening 72 at the other end thereof, generally coaxial with theopening 71. Opening 72 has an axially inwardly directed flange 73therearound formed integral with the base 12. A generally disc-shapedcover 74 is provided to sealingly fit within the opening 71 and, inconjunction with an O-ring 75, prevent leakage of oil therethrough. Thecover 74 has a coaxial opening therethrough with axially inwardly andoutwardly directed flanges 76 therearound forming a generally tubularelement coaxial with the opening through the flange 73 at the oppositeside of the base 12.

A shaft 80 is mounted in the openings formed by the flanges 73 and 76 bymeans of bearings 81 and 82. Bearings 81, which are press fit into theflange 76, have an oil seal 83 fixedly positioned at the outer edgethereof between the shaft 80 and the flange 76 to prevent leakage of oiltherethrough. Bearings 82 are the closed type incorporating a cover 84which is press fit into the opening 72 in the flange 73 to preventleakage of oil therethrough. In the present embodiment the shaft 80 hasthree eccentrics 85, 86 and 87 spaced axially apart therealong andformed as an integral part thereof. The eccentric 85 is positionedadjacent the inner edges of the flange 76 and the eccentric 87 ispositioned adjacent the inner edges of the flange 73. Hardened steeldisc-shaped wear plates 90 and 91 are positioned coaxial with the shaft80 between the eccentric 85 and flange 76 and between the eccentric 87and flange 73, respectively. The wear plates 90 and 91 prevent axialmovement of the shaft 80 and further prevent wearing of the base 12,which may be constructed of a relatively soft material such as aluminumand the like. The innermost ends of the flanges 73 and 76 havevertically oriented grooves 92 and 93, respectively, extendingdiametrically thereacross to provide for a flow of lubricating oil intoand out of the bearings 81 and 82.

Each of the eccentrics 85, 86 and 87 have bearings 95, 96 and 97 engagedcoaxially thereover with rollers 98, 99 and 100 engaged coaxially overthe bearings 95, 96 and 97, respectively. Each of the rollers 98, 99 and100 have a radially outwardly extending flange aproximately axiallycentered thereon, which flange engages a groove in the lower end of theplunger 55 associated with the rollers 98, 99 or 100. The threeeccentrics 85, 86 and 87 are positioned on the shaft 80 so that themaximum eccentricity thereof is located at approximately 120 intervals.

In the operation of the pump a driving force is attached to the shaft 80to produce rotation thereof. As the shaft 80 rotates, the eccentrics 85,86 and 87 cause the three plungers 55 to move radially outwardly and, asthe maximum eccentricity passes the lower portion of the plunger 55assocaited therewith, the plunger 55 is forced radially inwardly in thecylindrical opening 17 by the biasing spring 58. Thus, reciprocatingmovement is produced in each of the plungers 55 when the shaft isrotated. This reciprocating movement is sinusoidal in nature with theoutput pressure portion or flow rate of each stroke being illustrated inFIG. 7. Referring specifically to the plunger 55 illustrated in FIG. 4,as the plunger 55 moves radially inwardly in the cylindrical opening 17fluid is drawn through the openings 22 from the cavity 18, to fill theportion of the cylindrical opening 17 above the plunger 55. During thisinward movement of the plunger 55 the flexible ring 33 is held tightlyover the openings 32 by a combination of the suction in the cylindricalopening 17 and the springs 34. When the plunger 55 begins to moveradially outwardly the fluid in the cylindrical opening 17 is underpressure and the valve member 23 closes the openings 22 to prevent thefluid from flowing back into the cavity 18. The pressurized fluid isthus forced through the openings 32 and moves the flexible ring 53radially inwardly so that fluid is free to flow into the cavity 19 andthrough the outlet port 16.

Since each of the three plungers 55 is moving sinusoidally within thecylindrical openings 17 under the impetus of the shaft 80 and attachedeccentrics 85, 86 and 87 and since the pressure output, or flow rate,varies sinusoidally for each cylindrical opening 17 and associatedplunger 55 (as illustrated in FIG. 7), the total pressure, or flow rate,at the outlet port 16 follows a curve substantially as illustrated inthe solid line of FIG. 7. Also, the reciprocations of the plungers areequiangularly displaced (wtih 3 cylinders the angular spacing is Itshould be noted from FIG. 7 that the point at which adjacent pressurewaves cross, for example is 30 from the end of the first pressure waveand 30 beyond the start of the second pressure wave. Because the sine of30 is one-half, the sum of the pressure (the total pressure at theoutlet port 16) at these crossover points is equal to one, or the peakpressure of any of the pressure waves. Thus, the total pressure at theoutlet port 16 is a nearly constant pressure having a slight ripple orvariation with a frequency twice that of the three combined pressurewaves illustrated in FIG. 7. In a similar fashion the suction at theinlet port 15 is nearly constant.

Referring to FIG. 9, a graphic comparison of the output flow rate of theimproved pump (dotted line) to the output flow rate of a pump havingplungers driven by short connecting rods (full lines) is illustrated.The short, or low L/R ratios (where L equals the length of theconnecting rod and R equals the crank radius), connecting rods have atendency to produce flow rates in individual cylinders which moreclosely approximate sawtooth waves, rather than sine waves. Thecombination of these waves produce a total flow rate having thedistorted wave illustrated in FIG. 9 and the relatively widely varyingoutput pressure. As the length of the connecting rod increases (L/Rratio increases) the variations of the total flow rate decrease untilthe length approaches infinity, the individual flow rates becomesinusoidal, and the flow rate curve of the improved pump is reached. Thetotal flow rate curve illustrated by the full line in FIG. 9 is producedby a three cylinder pump having connecting rods with an L/R=2 /2.

It should be noted that the fluid being pumped comes in contact onlywith the head 11 and portions therein and, thus, only the head 11 andportions therein contacting the fluid need to be chemically compatibletherewith. Also, because of the in-line configuration the coring andcasting is all done in one plane and, therefore, greatly simplified.Thus, the overall construction of the pump facilitates the manufactureof a line of pumps wherein the heads are altered for various endresults, such as for pumping different types of fluids, variouspressures and amounts of flow, etc., while the base 12 remainssubstantially uniform.

In FIGS. 5 and 6 a different embodiment of the pump is illustratedwherein the spring 47, which provides a compression on the packing 45,is eliminated for reasons which will be apparent presently. In thisembodiment modified or new components are indicated with a similar ornew number and a prime added to indicate a different embodiment. Apacking cartridge 40, similar in shape to packing cartridge 40, has aplurality (in this embodiment, four) of openings therethrough extendinggenerally parallel with the axis of the cylindrical opening 17 andsubstantially centered over the packing follower 46. A plurality ofsmall pistons 51 are slidably engaged in the openings for axial slidingreciprocating movements. Flexible rings or seals 52' encircle each ofthe pistons 51 to prevent fluid from passing axially therealong. Thelower ends of the pistons 51' rest against the packing follower 48 whilethe upper ends are in communication with the cavity 19 and have outletfluid pressure thereon.

The packing 45 is most susceptible to movement relative to the plunger55 when the plunger 55 is moving axial- 1y into the cylindrical opening17. At this time fluid in the cylindrical opening 17 is under pressureand is being forced out of the cylindrical opening 17 through theopenings 32 and into the cavity 19. In the embodiment illustrated inFIG. 5 the fluid under pressure in the cavity 19 is in communicationwith the axially inner ends of the pistons 51' and produces an axiallyoutward force thereon, which is transmitted through the pistons 51 tothe packing follower 48. The packing follower 48 in turn maintains thepacking 45 under compression so that leaking does not occur between thepacking 45 and the plunger 55. It shouldbe understood that'the pistons51 are simply one embodiment for utilizing the output fluid pressure tomaintain a compressive force on the packing 45 and many otherembodiments might be devised by those skilled in the art. One example ofsuch an embodiment is to provide direct communication between the cavity19 and the packing follower 48 so that fluid passing through the cavity19 and under outlet pressure will provide a pressure directly on thepacking follower 48.

In FIGS. 9 and 10 another different embodiment of the pump isillustrated wherein modified or new components are indicated with asimilar or new number and a double prime to indicate a differentembodiment. Each of the plungers 55' is formed with a downwardly openingcavity 65' in the lower end thereof, rather than the groove described inthe first embodiment. The shaft 80 has three eccentrics 85, 86 and 87spaced axially apart therealong and formed as an integral part thereof.Each of the eccentrics 85, 86 and 87 has an arcuately shaped bearingshoe 66' slidably engaged thereon with a radially outwardly extendingtooth 67 formed as an integral part thereof. The shoe 66 is constructedso that an inner arcuate surface having a diameter equal to the diameterof the associated eccentrics 85 86 and 87 is concentric With an outerarcuate surface thereof. The rotation of the eccentries 85 86 and 87produces a relatively rolling movement between each of the shoes 66' andthe associated plungers 55, as illustrated in FIG. 10, thereby, greatlyreducing friction and wear. Further, the motion produced by the combinedrotary movement of each of the eccentrics 85, 86 or 87 and theassociated shoes 66' urge the plungers 55 in sinusoidally reciprocatingmovements,

Thus, an improved pump is disclosed which is relatively simple andinexpensive to manufacture since the entire housing can be cast and thecylindrical openings 17 can then be formed with a single tool operation.The present pump is relatively simple and quick to assemble since thevarious parts are all fitted within the cylindrical opening 17 and theshaft 80 is simply placed in the base 12 so as to contact the lower endsof the plungers 55 Because the cylinders are all in-line the overallconstruction of the pump is greatly simplified and the reliability andlife is greatly increased. In addition, the means for mounting the shaft80 in the base 12 provides for wear-resistant mounting of the shaft 80while allowing the base 12 to be constructed of a relatively inexpensiveand softmaterial. Further, the use of three cylinders and sinusoidallymoving plungers therein produces a relatively constant outlet pressure,or flow rate, and inlet suction. It should be understood that more thanthree cylinders might be utilized and 8 additional reductions of outletpressure variations can'b'e realized, for example While four cylindersproduce larger variations five or more will produce a smoother outletpressure if properly timed. Many other advantages and modifications maybecome apparent to those skilled in the art upon further considerationthereof.

What is claimed is:

1. An improved pump, comprising:

(a) a housing having joinable base 'and head portions;

(b) the head portion including a wall member defining elongated firstand second chambers, the first and second chambers being disposed inparallel alignment with the first chamber overlying the second chamber;

(c) a fluid inlet communicating with the first chamber and a fluidoutlet communicating with the second chamber;

(d) a plurality of openings alignably formed in the wall member toestablish fluid communication between the first and second chambers;

(e) removable insert means for each of said openings disposed entirelywithin said second chamber and in transverse relation to the first andsecond chambers, each removable insert means comprising: I

(I) tubular sealing means defining a pumping chamber; a

(2) inlet check valve means abutting the wall member and cooperable withthe associated opening and tubular sealing means for admitting fluidfrom the first chamber to the pumping chamber;

(3) outlet check valve means cooperable with the tubular sealing meansfor permitting fluid to flow from the pumping chamber to the secondchamber;

(4) the tubular sealing means and inlet and outlet check valve meansbeing constructed and arranged for joint assembly;

(f) the head and base portions being constructed and arranged to.cooperably retain the respective insert means when joined;

(g) a plunger reciprocally disposed in each pumping chamber;

(h) and means disposed in the base portion for reciprocating theplungers.

2. The pump defined by claim 1, wherein each tubular sealing meansfurther comprises packing encircling the associated plunger forsubstantially preventing fluid flow axially therealong.

3. The pump defined by claim 2, wherein each tubular sealing meansfurther comprises biasing means for maintaining a compression force onthe packing during reciprocating of the associated plunger. Y

4. The pump defined by claim 3, wherein the biasing means includes meansmounted in communication with the second chamber for receiving fluidpressure therefrom during compression strokes of the associatedplungenw.

. 5. The pump defined by claim. 1, wherein the plunger reciprocatingmeans comprises a drive shaft rotatably mounted in the base portion andeccentric means rotatably aflixed to the shaft and engageable with eachplunger.

6. The pump defined by claim 5, wherein the eccentric means includes amember having a generally circular outer periphery eccentricallyattached to theshaft and a'bearing mounted, generally annular. rollercoaxially aflixed in overlying relation to the periphery of said member;

7. The pump defined by claims, wherein the eccentric means includes amember having a generally circular outer periphery eccentricallyattached to the shaft and a bearing shoe slidably engaged on the outerperiphery of said member with a radially outwardly extending toothengaged in a downwardly opening cavity inthe lower end of the plunger. vI

8; The pump defined by claim 5, including springbia s ing means mountedin the housing and 'urging'the plunger into engagement with'theeccentric means.

9. The pump defined by claim 5, wherein that portion of the base portionin which the shaft is mounted is constructed of a relatively softmaterial and relatively hard annular wear elements are coaxiallypositioned with respect to the shaft between radially outwardlyextending portions of the shaft adjacent both ends thereof and the baseportion.

10. The pump defined by claim 9, wherein bearings mounting the shaft inthe base portion are positioned coaxial with the shaft axially outwardlyfrom each wear element and grooves are formed in the base portionadjacent each wear element for the circulation of lubricant into saidbearings.

11. The pump defined by claim 5, wherein the eccentric means and plungerare mounted in relative rolling engagement and cooperating groove andflange portions are formed therebetween to substantially preventrelative transverse movements.

12. The pump defined by claim 11, having three openings in the wallmember, the plunger engaging means constructed and arranged to effectequiangularly displaced reciprocations of the plunger.

References Cited UNITED STATES PATENTS 3,260,217 7/1966 Thresher 4l75672,218,928 10/ 1940 Towler et a1. 74-55 2,523,847 9/1950 lRussey 308-1633,109,378 11/1963 Baines 417-539 3,330,217 7/1967 Baur et al 417-4543,371,936 3/1968 Beaudette 277-117 1,070,706 8/1913 Luitwieler 4l75392,059,758 11/1936 Stearns 4l7454 FOREIGN PATENTS 993,887 6/1965 GreatBritain 417-569 CARLTON R. CROYLE, Primary Examiner J. J. VRABLIK,Assistant Examiner US. Cl. X.R.

